RICIN

Ricin is just about the easiest, and at the same time, most toxic poison that a criminal can

make. Less than a milligram (1/1 ,000 of a gram) injected or inhaled will kill a person several

times over. For individual killings, it has the advantage of being undetectable in toxicology

scans since the poison is a catalyst the starts a chain reaction in the body, and is destroyed

before the symptoms begin to show.

With properly sized and dispersed dry particles, ricin is at least lOx more toxic than the most

potent nerve gas. A 1% water solution atomized with a small explosive burster has the same

effectiveness as sarin nerve gas. The only disadvantage ricin has is the time it takes for the

victims to die is about 1 - 2 weeks. So you won't have the quick tactical effect of nerve gas. But

this can also be good in that, using a covert dissemination, the criminal has time to escape

before the attack is detected.

The information presented below is from a US Patent #3,060,165, assigned to the US Army.

Tips

Here's a few things you need to know to make your production go much easier.

1 . The seeds are readily available through wholesale seed suppliers for about $20 for a

pound of seeds. Castor bean seeds are very tough to crack or peel. Soak them for an

hour in a solution of 2 tablespoons lye in 1 cup water. Then use pliers to crack the shell.

The shell will peel of the bean easily then.

2. Use a 1/2 cup of acetone to every ounce of bean pulp. Blend well. Let sit for several days

with occasional shaking. Pour off the acetone and add an additional 1/2 cup of acetone

and repeat. This will remove almost all the castor oil from the seeds.

3. The patent doesn't mention it, but you can use magnesium sulfate (Epsom salt) instead of

sodium sulfate. Epsom salt is easily available in any drug store for just about a dollar a

pound.

4. Use a plastic membrane filter if you can get them. The ricin forms a layer that is difficult to

remove from a regular coffee paper filter without scraping off fibers as well.

5. Wear a gas mask and gloves. Try to keep the ricin wet at all times to avoid generating

any dust (DEADLY!). And always shower and change clothes after handling.

Preparation

Ricin is a protoplasmic poison prepared from castor beans after the extraction of castor oil

therefrom. It is most effective as a poison when injected intravenously or inhaled, the latter

requiring extreme commutation and small particle size to be effective, It is believed that the

toxic action is catalytic rather than stoichiometric which probably accounts for the high toxicity

of the agent.

Because of its relative instability ricin must be handled with extreme care. In neutral aqueous

solution it is stable only up to 60"-75" C., and in solid form up to 100"- 110" C., although for

short exposures, temperatures up to 130" may be tolerated. It is sensitive to acids, alkalis and

halogens and may also be inactivated by mechanical working such as grinding or pulverizing.

These factors are of great importance in developing a satisfactory method for preparing the

material.
Although ricin has been prepared in crystalline condition in the laboratory in small quantities, it

becomes necessary, for purposes of toxicological warfare, to prepare relatively large quantities

in a high state of purity. This necessitates that as much as possible of the non-toxic material

present be removed in the process.

In preparing the protein material, the castor beans are first ground and pressed to remove most

of the oil. The pressed cake still retains about 15% oil and this may be removed by means of

solvents which will extract an additional 150 pounds of oil per ton of beans and reduce the oil

retained in the cake to a little over 1%. In the event that the expressing step is supplemented by

solvent extraction, it is important to prevent detoxification of the protein during the solvent

removal step. If residual solvent is removed from the ground beans by blowing with steam,

considerable detoxification results. Blowing with nitrogen effectively prevents detoxification but

is expensive when carried out on a large scale.

After the oil has been removed, the pressed cake or pomace is extracted by agitating with

water at a pH of 3.8+-0.1 at 25" C. which removes substantially all of the toxic protein. The

extraction process is operative within a pH range of about 3 to 4.5 although the preferred range

is about 3.5 to 4. The optimum operating point is a pH of 3.8+-. 1 , as indicated above. A careful

pH control is essential in order that as much non-toxic protein as possible may be eliminated

and also that the filtration rate may be held at a satisfactory value. Either HCI or H2S04 may be

used to get the desired pH for the extraction water, but H2S04 is preferred due to its lower

corrosion rate and ease of handling in concentrated form. The acid should be used in

reasonably dilute form to prevent undue local concentrations during its addition. A 5%

concentration is satisfactory.

Following the extraction, the slurry is filtered using either a conventional recessed plate filter or

a continuous string discharge vacuum filter. With the latter about 7% of filter aid, based on meal

weight, was found necessary for satisfactory filtration.

The filtrate from the water extraction step, which contains the ricin, was treated with a 16.7%

solution of Na2S04 to precipitate the protein. This solution is composed of 20 pounds of salt in

1 00 pounds of water and the amount used was such that the salt content equaled 20% of the

filtrate weight. This amount and concentration of salt solution was about optimum considering

the factors of cost and toxin recovery. Somewhat higher concentrations and larger amounts of

solution can be used, however.

The precipitation process is not limited to the use of Na2S04 since a saturated solution of NaCI

can be used successfully, but Na2S04 solution gives better nitrogen fractionation, more rapid

precipitation, and can be operated under wider pH limits. It is desirable to raise the pH to about

7-8 before precipitation as this gives better recovery and greater non-toxic nitrogen removal.

The pH was raised to this value by using NaOH or Na2C03 the latter being preferred. The

base used was quite dilute in order to prevent detoxification due to high local concentrations in

the solution. A 5% solution of NaOH was used, whereas with Na2C03 a 12% solution was

preferred.

In general, this higher pH during precipitation gave a greater non-toxic nitrogen fractionation

and at the same time maintained the toxin loss at less than 2%. After precipitation, the slurry

was filtered using from 1 to 4% filter aid, based on slurry weight, for satisfactory filtration, the

amount of filter aid needed being dependent on the type of press used. Washing the filter cake

with Na2S04 solution removed additional non-toxic nitrogen which is desirable. In this washing

step a 16.7% solution of Na2S04 was again used. This washing step removed an additional

15% of non-toxic nitrogen from the cake.

After filtration the filter cake which contains the ricin in combination with the Na2S04 may be

dried and slurried with CCI4 to separate the ricin by flotation. Separation of the ricin after a

single precipitation and washing step is possible, but it is preferred to carry the process through

an additional extraction and precipitation step. This is accomplished by slurrying the filter cake
in three times its weight of water and the pH of the slurry is again brought to 3.8+-. 1 by means

of 5% H2S04 The slurry is filtered and a second precipitation is brought about by adding

Na2S04 solution. Although pH control here is not wholly essential it is advantageous to bring

the pH to approximate neutrality by adding 12% Na2C03.

A precipitation time of 45 minutes was necessary to obtain complete removal of the toxin. In

filtering out the precipitate, no filter aid was used and the filter cake was washed with Na2S04

solution on the filter whereby an additional amount of non-toxic nitrogen was removed from the

cake. This washing was effective only the first time and repeated washings had little effect in

removing further non-toxic nitrogen.

The ricin-Na2S04 precipitate was dried at about 50" to 60" C. on a hot air tray dryer. The dried

product was ground to pass a 40 mesh screen and agitated with 5 times its weight of CCI4

which served the separate the ricin from the Na2S04 by flotation. After settling, the ricin was

skimmed off the top. This reduced the Na2S04 content of the mixture from a previous 40 to

50% down to 15 to 18%. About 1 to 2% of nitrogen remained in the Na2S04 salt which could

then be used for subsequent precipitations.

The final precipitation produced a particle size of 1-2 mu. On drying the wet cake, however, the

ricin cemented together forming larger particles. These could not be broken down to their

original size by ordinary grinding methods and since a very line particle size was necessary in

order that the product might be used as a toxic weapon, it was thought desirable to seek some

method to prevent the agglomeration or cementing process that took place on drying.

To attempt lo affect this result, physical conditions prevailing under the precipitation process

were changed. This included changing the temperature of precipitation and the rate of agitation.

Other changes included precipitation with only partial saturation of Na2S04 and the use of

wetting and seeding agents. None of these expedients produced any significant improvement in

particle size. Ordinary dry ball and hammer milling of the dried ricin produced considerable
detoxification perhaps due to the generation of excess heat. The use of CCI4 slurry plus the

use of low temperature and low moisture content of the ricin reduced detoxification during ball

milling.

Spray drying proved to be an even better method of securing a reasonably small particle size.

Best results were achieved by using a solution having about 20% solids, an inlet temperature of

150" C. and an atomizing air pressure of 150 to 180 p.s.i. The particle size secured was 6 to 8

mu.

The best means of securing a small particle size was by air grinding. This was carried out in an

apparatus having a chamber with conical top and bottom. The material to be ground has been

fed into this chamber and is withdrawn from the bottom and forced back into the center of the

chamber tangentially through a venturi. Compressed air of about 100 p.s.i. was fed to the

venturi to provide the grinding force. The fines are drawn off the top and the large particles

settle to the bottom to be recirculated and reground. This process produced particles having a

mass median diameter of 2.5 to 3.5 mu.

Numerous variations are possible in the several steps of the process commencing with the

water extraction and precipitation which may be a single or multiple step. Although a single

extraction step can be used, as indicated before, some process modifications are necessary for

its successful operation on a plant scale. Double extraction proved to be quite efficient but

additional steps beyond the second extraction step were not found necessary.